So, any idea what the lumen output of the GT4 would be? Or should I just go for the MS18? Also, is there any GB list I can register for this light?
For shear lumens you need the MS18, the GT4 will put out one-third of that one. The MS18 may even be more compact and lightweight. So what are the advantages of the GT4 then?
*more runtime (obviously with the lower output), even with the lower capacity 18650’s
*your own choice of batteries, as opposed to a fixed battery pack
*probably sustainable output at 30K+ max until the batteries are empty
*no noisy fan! I think that is the biggest disadvantage of the MS18, which is also an extra part that could fail. The MS18 may be not be very rain-proof (but that is my guess, the specs state a waterproof fan)
*I’m sure it will be way cheaper
I don’t think there is a group buy for the GT4, at least not yet
Man 30K is still nothing to sneer at, specially if its sustained
And you can, as a plus, use the GT4 as a door stop once the cells die. 
… She’s a Brick, house, she’s the one, the only one… (oops, sorry)
Officially the goal is 20k lumens for the production light.
It does not fit in my sphere so I have not been able to get good lumen readings yet, that will have to wait until VOB gets it for his review.
A 4” to 3” reducer is about $11 at Home Depot. Just sayin…
Yes but the sphere is not calibrated for it and a 4” is still not technically large enough to fit the GT4. It is not a bad idea though, I could pick one up next time I am over there just to play with.
I suppose I could recalibrate it for the reducer but not having tested this I have no idea how accurate it will be since a lot of the light will directly hit that reducer and bounce back up towards the light. In theory it should not matter once calibrated but I would need to do some testing to know for sure.
You would need at least a 5” adapter. I don’t see 5” to 4”, but I do see a 6” to 4”.
Will that adapter give an accurate reading, though? Obviously you have to recalibrate the Tube with a calibration light. What concerns me is the light that is bounced back in the neck instead of going down the smaller tube. Maybe the calibration light needs to be inserted near the edge so that some of it’s light gets bounced back? IDK, it seems it’s a bit more complicated than just adding an adapter.
Re-calibrating with the reducer in place will not fix it. Because light from the outer part of the reflector will not have the same chance to reach the detector as light from the inside, the integration is decreased, it will only be correct if the calibration light has the same size and beamshape as the light to be measured, but then a device is not needed, you could compare lux on a wall.
Yeah, that is what I was thinking as well.
I keep hoping that lumintop will give me some updates so I can finish with what I need from the prototype and send it on to VOB.
According to everything already said it will never be correct in a PVC light box anyway.
Nor, according to reading from the pro’s, will an actual lumisphere. Such is life.
So, perfection notwithstanding, a reasonable facsimile will suffice….
I just got back from rying to take some beamshots at the creek, I will look at them tomorrow to see how they came out. Didn’t have any good comparison lights to shine it with but it is the same location as the GT and GT70 shots.
It lights EVERYTHING up, it is a massive thick beam of light.
It is hard to gauge raw throw since the beam is just so big but it lit up everything I pointed it at without an issue. Funny how the GT70 seemed so bright, this is another league. It literally hurts to even look at the spot it shines. This comes from a guy used to 10k+ lumen flahlights.
The most impressive thing was the thermals, we had it on for ~5 minutes and it was still not that hot and had not started stepping down. Just the breeze from moving around was enough to keep it remarkably cool considering the power. I am very happy with the thermal performance.
Ok, here are the beamshots from last night, not the best by any means, I was worried about this. It is just so bright it blows out the camera. It lights EVERYTHING up.
This is with the LED’s swapped out for 4000k, 80cri LED’s since the LED’s they sent died due to a design flaw in the prototype. P2 bin 70cri LED’s will be brighter but lower cri of course.
Here is a shot with the exposure turned down some so it would not blow out as much:
And so you can get an idea of the beam shape:
Dude, no offense but that’s really a horrible place to try and show the beam of a big thrower big lumens light. Far too constrictive and far too close. A football field, a flood plane, I know for a fact there are a LOT better places in the area for such a light to be exploited. And the camera only blows out when you don’t use the settings properly. Sorry but again, fact. But hey, you tried. The straight up beamshot does show the beam definition pretty well.
Oh, trust me I know it is a bad location, remember I did say that I was waiting to let VOB do the beamshots? Also, I left the camera on roughly the same settings as the shots in the past, it blew out the photo using those settings, see the second picture? I adjusted them for that one
Around me there are not really any other good locations I can get access to without risking the police showing up within a reasonable distance. I drove around for hours one time looking for a better spot but all of them had issues in some form or another, you really need to be up high to get a good shot, otherwise the light hitting the ground near the camera ruins the shot. Around here that is a hard thing to find with any kind of distance before a tree line.
Thank you very much for the beamshots. Do you have a link or reference to your other shots of the GT/GT70? Where they shot with the same camera settings?
They should be posted on the first page of both of those threads but I don’t have them on me right now.
Same camera, roughly the same settings. Those lights were a long time ago so hard to remember for sure. Although I edited most of the pictures in post to closer resemble what I saw in real life (generally making it darker as all of them tended to appear brighter then they were in the raw photos).
Nice…. 
Thanks TA.
I usually use a 1/2 second exposure at ISO 1600 with an F5.6 on my smaller camera’s (started using the G1X years ago and try to keep using it for consistency), exposure compensation at 0.0 not + 2/3’rds like you have there. Use a tripod, go longer shutter and pull the ISO down for a cleaner clearer shot. I can’t fix that you use a Nikon so you’ll just have to make do. 
lol, yeah I could use a tripod but just didn’t have the time to bring it and set it all up. This was a hop in the car, snap a pic, come home 10 minutes before bed type of thing lol.
Plus the spot was so bad for the beamshot I didn’t feel like trying to polish poop lol.